This invention relates to a method of retarding or minimizing the effects of corrosion when N-methyl pyrrolidone is utilized in a petroleum processing operation.
N-methyl pyrrolidone (hereinafter referred to as NMP) has been known to be useful in various petroleum hydrocarbon compositions and processing operations. Such uses include that of a solvent for the separation of olefins, for the recovery of acetone from petroleum gas, for the extraction of naphthalenic hydrocarbons from various hydrocarbon mixtures, as a chemical reaction medium, as a polymer solvent, for use in industrial cleaning, for decolorizing petroleum oils and waxes, in paint removers, as a deicer for jet fuels and gasoline etc. Perhaps the most important and widest industrial use of NMP is as an aromatic extraction solvent in various petroleum refining processes. Illustrative processes are for the separation of benzene, toluene, and xylene or the well-known BTX process, the recovery and separation of relatively pure single-ring aromatics such as xylene, benzene and toluene from relatively light hydrocarbon mixtures known in the industry as the Arosolvan process, and in the extraction of aromatics from lube oil fractions in order to produce lube oils of relatively high VI and UV stability. Within the past ten years or so, a considerable amount of industrial research and development has been expended by the petroleum industry towards the utilization of NMP in lube oil deasphalting, extraction and dewaxing. See for example U.S. Pat. Nos. 3,843,515; 4,013,549; 4,057,491; 4,125,458 and 4,168,226.
While the use of NMP in various petroleum processes has been growing and is for the most part quite successful, there has been one problem associated with its use, that is the corrosion which develops in various processing units.